sys/filedesc.h

This structure is used for the management of descriptors. It may be shared by multiple processes. A process is initially started out with NDFILE descriptors [XXXstored within this structureXXX], selected to be enough for typical applications based on the historical limit of 20 open files (and the usage of descriptors by shells). If these descriptors are exhausted, a larger descriptor table may be allocated, up to a process' resource limit; [XXXthe internal arrays are then unusedXXX]. The initial expansion is set to NDEXTENT; each time it runs out, it is doubled until the resource limit is reached. NDEXTENT should be selected to be the biggest multiple of OFILESIZE (see below) that will fit in a power-of-two sized piece of memory.

#define NDFILE 25